Interface circuit

ABSTRACT

Devices and methods are provided where a first signal and a second signal are received. The second signal may be a single-ended signal and may be selectively converted to a differential signal based on a type of the first signal.

RELATED APPLICATIONS

The instant application claims priority of German Patent Application No.102014114499.6, which was filed on Oct. 7, 2014. The entire contents ofthe identified German Patent Application No. 102014114499.6 are herebyincorporated herein by reference.

BACKGROUND

Interface circuits may be used in electronic devices to transmit andreceive signals, for example signals related to data transmission likedata signals, clock signals or chip select signals. An example for suchan interface circuit is a microsecond channel (MSC) interface. The MSCinterface is an interface which may be used to couple a master devicewith one or more slave devices. The MSC interface uses, in a downstreamdirection (from master device to slave device) a chip select (CS) signal(selecting, for example, one of a plurality of slave devices), a serialdata in signal (SI) and a clock signal (CLK), and, in an upstreamdirection (from slave device to master device) a serial data signal(SDO). The serial data and clock signals may be configured to berepresented as single-ended signals or differential signals, inparticular low voltage differential (LVD) signals, while, for example,the chip select signal according to the MSC interface is always asingle-ended signal. Single-ended signals may be processed in theinterface differently from differential signals. In some circumstancesthis may lead to timing problems, for example when sampling asingle-ended signal like the chip select signal in an MSC system basedon a differential signal, for example a differential clock signal in anMSC system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a block diagram of an interface circuit according toan embodiment.

FIG. 2 illustrates signals and parts of devices for illustratingoperation of some embodiments.

FIG. 3 is a diagram illustrating an interface circuit according to anembodiment.

FIG. 4 is a diagram illustrating a single-ended-to-differentialconverter according to some embodiments.

FIG. 5 is a circuit diagram illustrating an interface circuit accordingto an embodiment.

FIG. 6 is a circuit diagram illustrating a single-ended-to-differentialconverter according to some embodiments.

FIG. 7 is a flow chart illustrating a method according to an embodiment.

DETAILED DESCRIPTION

In the following, various embodiments will be described in detailreferring to the attached drawings. It is to be noted that theseembodiments are given only for illustration purposes and are not to beconstrued as limiting the scope of the present application.

Features of different embodiments described in the following or shown inthe drawings may be combined with each other and are specifically notedotherwise. Also, a modification or variation described with respect toone of the embodiments may also applicable to other embodiments.

While embodiments are described and illustrated as comprising aplurality of features or elements, it is to be noted that this is not tobe construed as indicating that all those features or elements arenecessary for implementation of embodiments. Instead, in otherembodiments some of the features or elements shown or described may beomitted and/or replaced by alternative features or elements. In otherembodiments, additionally or alternatively additional features orelements to the ones described or illustrated may be provided. Anyconnection or couplings illustrated in the drawings or described hereinmay be a direct connection or coupling, i.e. a connection or couplingwithout additional intervening elements (for example a metal wire orpart of a metal layer), or may be an indirect connection or couplingcomprising one or more additional intervening elements, as long as thebasic function of the connection or coupling, for example to transmit acertain kind of information or signal or to provide a certain controlfunction, is essentially maintained.

Some embodiments relate to interface circuits. An interface circuitaccording to some embodiments may comprise a first signal input toreceive a first signal and a second signal input to receive a secondsignal. The second signal may be a single-ended signal, while the firstsignal may either be a single-ended or a differential signal. In someembodiments, depending on whether the first signal is a single-endedsignal or a differential signal, the second signal may be selectivelyconverted to a differential signal prior to being further processed. Forexample, the second signal may be converted to a differential signalwhen the first signal also is a differential signal. The term“selectively performing a single-ended differential conversion” and thelike also is intended to cover cases where the single-ended signal isalways supplied to a single-ended-to-differential converter, but theoutput signal of the single-ended-to-differential converter is only usedin the selected cases when the conversion is to be performed. Othertechniques may also be employed.

Turning now to the drawings, in FIG. 1 a block diagram of an interfacecircuit 10 according to an embodiment is illustrated. The block diagramof FIG. 1 is to be regarded as schematic only, and elements shown may bearranged and coupled in a different manner than shown. Interface circuit10 in embodiments may serve as an interface of an integrated circuit orother device. In some embodiments, interface circuit 10 may be an MSCinterface circuit or part thereof.

In the embodiment of FIG. 1, interface circuit 10 comprises a firstsignal input 11 to receive a first signal and a second signal input 12to receive a second signal. In the embodiment of FIG. 1, the secondsignal is a single-ended signal, while the first signal may selectivelybe a single-ended signal or a differential signal.

In the embodiment of FIG. 1, in case the first signal is a single-endedsignal, the second signal (which is also a single-ended signal) may beprocessed by processing circuitry 16 in unaltered form, and the firstsignal may be processed by processing circuitry 13. For processingsingle-ended signals, processing circuitries 13, 16 may essentially havethe same design, and thus cause the same or similar delays. In case thefirst input signal is a differential signal, a selection circuit 14 maycontrol a single-ended-to-differential converter 15 to convert thesecond signal to a differential signal. The differential signals may below voltage differential (LVD) signals. In this case, the first signal(in this case a differential signal) is processed by processingcircuitry 13, and the second signal after the conversion bysingle-ended-to-differential converter 15 (also a differential signal)is processed by processing circuitry 16. Also for this case, processingcircuitries 13, 16 may have a same or similar design. Processingcircuitries 13, 16 in some embodiments may, for example, compriseamplifiers or buffers, just to give examples. Therefore, also in thiscase in some embodiments the delay caused by processing circuitries 13,16 may be the same or similar, such that a delay difference may belimited to a delay difference caused by single-ended-to-differentialconverter 15. In some embodiments, in this way a delay between thesignals may be reduced compared to some conventional solutions.

In some embodiments, the first signal may be a clock signal, and thesecond signal may be a signal to be sampled based on the clock signal,for example a chip select signal. In such embodiments, in some caseslimiting the delay difference may help to ensure correct sampling. Inother embodiments, other techniques may be employed.

To illustrate issues associated with different delays for differentsignals further, FIG. 2 shows various example signals and devices. Forexample, an MSC interface circuit may receive a differential clocksignal 20, a differential data signal 21 and a single-ended chip selectsignal 22. In an interface, differential clock signal 20 may be receivedat pads pad_clk_p and pad_clk_n and fed to a differential amplifier 23to output a signal dig_clk. Differential amplifier 23 may cause a delaytd_diff.

In a similar manner to differential clock signal 20, data signal 21 inthe example of FIG. 2 is received at pads pad_se_p, pad_se_n and fed toa differential amplifier 24 to produce an output signal dig_si.Amplifier 24, for example a differential operational amplifier,introduces a time delay td_diff which may be approximately the same asthe delay introduced by amplifier 23.

Single-ended signal 22 is received at a pad pad_cs and amplified by asingle-ended amplifier 25 to produce a signal dig_cs. Single-endedamplifier 25 may introduce a time delay td_se that may be different fromthe time delay td_diff introduced by differential amplifiers 23, 24.

In FIG. 2, a time is designates a setup time, and a time th designates ahold time. A setup time is a time a signal is asserted prior tosampling, and a hold time is a time the signal remains after thesampling. If the setup time or the hold time falls below a respectivethreshold time, incorrect sampling may occur. In the example used inFIG. 2, data signal 21 and chip select signal 22 on a receiver side areto be sampled based on rising edges of clock signal 20. On thetransmitter side (signals 20 to 22) the rising edge is approximately inthe middle of a time period where signal 21 or 22 remains constant,which may lead to sufficiently large setup and hold times. As shown onthe right side of FIG. 2, this may change due to the delays introducedby amplifiers 23 to 25. On the right side of FIG. 2, 26 shows an examplefor the signal dig_clk, which is offset from the original differentialclock signal 20 by time difference td_diff. In a similar manner, curve27 shows an example for signal dig_se, which is offset from the originaldata signal 21 again by td_diff. Curve 28 shows an example for signaldig_cs, which is offset from the original signal 22 by td_se, which inthis example is larger than td_diff. As signals 26 and 27 experience thesame delay, the sample and hold time essentially remain unchangedcompared to the transmitter side (left side of FIG. 2). However, due tothe different delays td_se and td_diff, sampling of signal 28 withsignal 26 may be more prone to errors, as in the example the setup timeis becomes very small.

Some embodiments, as already mentioned with respect to the embodiment ofFIG. 1, may employ a selective single-ended differential conversion tomitigate such issues. In other embodiments, other techniques may beused.

In FIG. 3, an interface device according to a further embodiment isillustrated. The interface device illustrated in FIG. 3 may be an MSCinterface or part thereof, but also may be used to implement other kindsof interfaces. The interface circuit illustrated in FIG. 3 mayselectively receive a differential clock signal pad_clk_diff_p,pad_clk_diff_n at pads 32, 33 or a single-ended clock signal pad_clk_seat a pad 36. Furthermore, the interface circuit illustrated in FIG. 3may receive a single-ended chip select signal pad_cs at a pad 311, whichis an example for any kind of single-ended signal.

A signal dig_se_en fed to a terminal 30 may switch the interface circuitof FIG. 3 between a first mode of operation where the differential clocksignal is received at pads 32, 33 and a second mode of operation wherethe single-ended clock signal is received at pad 36. The enable signaldig_se_en is fed to AND-gates 38 and 316 and additionally to an inverter31 which feeds the inverted signal dig_se_en to AND-gates 35 and 314.

Next, the first mode of the embodiment of FIG. 3 where the clock signalis single-ended (i.e. fed to pad 36) will be discussed.

In this case, a logic zero is fed by inverter 31 to AND-gates 35 and314, such that they always output a logic zero. Furthermore, a logic oneis fed to AND-gates 38 and 316.

The single-ended clock signal provided to terminal 36 is fed, forexample, to a Schmitt trigger 37 or other type of slicer having adefined threshold voltage and/or hysteresis. Schmitt trigger 37introduces a delay td_se. The output of Schmitt trigger 37 is then fedto AND-gate 38. As the other input of end gate 38 is provided with alogic one, the signal from Schmitt trigger 37 is essentially forwardedby AND-gate 38 to an OR-gate 39 and output as signal dig_clk at aterminal 310.

The single-ended chip select signal received at pad 311 is fed to aSchmitt trigger 315 or similar device, e.g. slicer, which may bedesigned similarly to Schmitt trigger 37 and may introduce essentiallythe same delay td_se. The output of Schmitt trigger 315 is fed toAND-gate 316 and, as the other input of AND-gate 316 receives a logicone from terminal 30, is essentially forwarded to an OR gate 317 andoutput at terminal 318 as signal dig_cs. Therefore, both thesingle-ended clock signal and the single-ended chip select signalexperience essentially the same delay td_se. Further, the subsequentelements 38, 39 on the one hand and 316, 317 on the other hand maycorrespond to each other, i.e. have similar or the same design andtherefore also introduce similar delays. In other words, delaystd_dig_clk and td_dig_cs may also be essentially the same. Consequently,signals dig_clk and dig_cs may have experienced essentially the samedelay. This in embodiments may, for example, ensure a correct signalsampling of signal dig_cs based on signal dig_clk.

Next, the second mode of operation when the clock signal is adifferential signal will be discussed. In this case, dig_se_en fed toterminal 30 may, for example, be a logic zero, such that a logic zero isfed to inputs of AND-gates 38 and 316, which, therefore, always output avalue of zero. Furthermore, through inverter 31, a logic one is fed toAND-gates 35 and 314, such that output signals of differentialamplifiers 34, 313 are essentially forwarded to OR-gates 39, 317 andfrom there (as AND-gates 38, 316 supply a zero) essentially forwarded toterminals 310, 318.

The differential clock signal, as already discussed, is received at pins32 and 33 and amplified by the aforementioned differential amplifier 34,and the output signal of amplifier 34 is provided to AND-gate 35. Thisintroduces a time delay td_diff. The subsequent elements again introducethe time delay td_dig_clk.

Moreover, the single-ended chip select signal received at pin 311 is fedto a single-ended-to-differential converter 312, converting thesingle-ended signal pad_cs to a differential signal cs_d_p, cs_d_n.

This conversion at converter 312 introduces a delay td_conv. The thusgenerated differential signal cs_d_p, cs_d_n is fed to the alreadymentioned differential amplifier 313. Differential amplifier 313 mayhave a similar or same design as a design of differential amplifier 34and may introduce a delay td_diff which is substantially the same as thedelay td_diff introduced by differential amplifier 34. As alreadyexplained, the output of differential amplifier 313 is then essentiallyforwarded to terminal 318 to be output as signal dig_cs. This forwardingvia elements 314, 317 introduces a delay td_dig_cs which may beessentially the same as the delay td_dig_clk introduced for the clocksignal.

Therefore, in the embodiment of FIG. 3, in the second mode, the delayintroduced for the differential clock signal is td_diff+td_dig_clk, andthe delay introduced for the single-ended signal (e.g. chip select) istd_conv+td_diff+td_dig_cs. Therefore, in embodiments the difference intime delays may essentially correspond to td_conv. In some embodiments,td_conv may be small (for example by a corresponding design of converter312), which in embodiments may help to reduce the time delay differenceand may, for example, help to assure a correct sampling of signal dig_csbased on signal dig_clk.

Next, with reference to FIG. 4, an example for asingle-ended-to-differential converter 44, in the example shown asingle-ended-to-low-voltage differential (LVD) converter according tosome embodiments will be discussed. While a specific implementation of asingle-ended-to-differential converter will be discussed in FIG. 4, thisserves only for further illustration, and othersingle-ended-to-differential converters may also be used in otherembodiments.

In the embodiment of FIG. 4, pads 40, 41 serve to receive a differentialsignal, for example a differential clock signal, and may correspond topads 32, 33 of FIG. 3, and an amplifier 42 serves to amplify thedifferential clock signal and may correspond to amplifier 34 of FIG. 3.A pad 43 in the example of FIG. 4 serves for receiving a single-endedsignal, for example a single-ended chip select signal, and maycorrespond to pad 311 of FIG. 3. Single-ended chip select signal is thenprovided to single-ended-to-differential converter 44, which will beexplained in more detail below and which may be an implementationexample of converter 312 of FIG. 3, but may also be used in otherembodiments. An output of converter 44 is provided to an amplifier 422,which may correspond to amplifier 313 of FIG. 3, and additionally anAND-gate 423 is illustrated at an output of amplifier 422 which maycorrespond to AND-gate 314 of FIG. 3. Other elements of the embodimentof FIG. 3 not explicitly illustrated in FIG. 4 may also be present inFIG. 4, and FIG. 4 focuses on a possible implementation ofsingle-ended-to-differential converter 44.

For single-ended-to-differential conversion of the signal pad_csreceived at pad 43, the signal is fed to a device like a Schmitt trigger410 or other type of slicer having, for example, a defined threshold anddefined hysteresis to provide a digital signal with two possible values.Based on this signal, switches 417 to 420 which are coupled asillustrated in FIG. 4 are controlled. In particular, switches 417 and420 are controlled by the output signal of Schmitt trigger 410, suchthat they are closed when the chip select signal corresponds, forexample, to a logic one and opened when the chip select signalcorresponds to a logic zero. Switches 418 and 419 are controlled by theoutput signal of Schmitt trigger 410 after the output signal has beeninverted by an inverter 416, such that switches 418, 419 are open whenswitches 417, 420 are closed and vice versa. Switches 417 and 418 areprovided with a first voltage level by an amplifier 414, and switches419, 420 are provided with a second voltage level by an amplifier 415.Therefore, depending on the state of the single-ended chip selectsignal, either the first voltage level is provided to the positive inputof amplifier 422 and the second voltage level is provided to a negativeinput of amplifier 422 (when switches 417, 420 are closed), or thesecond voltage level is provided to the positive input of amplifier 422and the first voltage level is provided to the negative input ofamplifier 422 (in case switches 418, 419 are closed). In this way, adifferential signal is provided to amplifier 422.

Furthermore, as will be explained next, converter 44 is adapted toprovide the first and second voltage levels, such that a common modevoltage thereof corresponds to a common mode voltage of the differentialclock signal provided to pads 40, 41. In this way, for example whenconverter 44 is used as converter 312 in FIG. 3, amplifiers 34, 313 areprovided with signals having a same common mode voltage, whichessentially corresponds to setting a same operating point for amplifiers34, 313. This additionally may help to make the time delays introducedby amplifiers 34, 313 essentially the same.

To this end, the signals at pads 40, 41 in the embodiment of FIG. 4 arecoupled to a positive input of an amplifier 47 via resistors 45, 46. Anoutput of amplifier 47 is fed back to a negative input of amplifier 47via a resistor 49. Furthermore, the negative input of amplifier 47 iscoupled to ground via a resistor 48. Resistors 45 and 46 may have a sameresistance value. Also, resistors 48 and 49 may have a same resistancevalue, although this need not be the case.

Furthermore, the output of amplifier 47 is provided to a resistivedivider comprising resistors 411, 412, 413 coupled between the output ofamplifier 47 and ground. Resistors 411, 413 may have a same resistancevalue, while resistor 412 may have a different resistance value comparedto resistors 411, 413. Other configurations may also be possible. A nodebetween resistors 411 and 412 is coupled with a positive input of thealready mentioned amplifier 414, and an output of amplifier 414 is fedback to a negative input of amplifier 414. A node between resistors 412and 413 is coupled to a positive input of amplifier 415, and an outputof amplifier 415 is fed back to a negative input of amplifier 415.

To illustrate further, via resistors 45 and 46 a common-mode voltage Vcmof the differential signal at pads 40, 41 is provided to the positiveinput of amplifier 47. Amplifier 47 then outputs essentially two timesthis common-mode voltage Vcm. Through the use of resistive divider 411to 413, amplifier 414 then outputs the common-mode voltage Vcm plus adifferential voltage Vd, and amplifier 415 outputs the common-modevoltage Vcm minus the differential voltage Vd, such that signals outputby converter 44 have the same common-mode voltage Vcm as the signalsupplied to pads 40, 41. Other implementations may also be used.

In FIG. 5, a circuit diagram illustrating an interface device accordingto a further embodiment is shown. While, in order to avoid repetitionsin the description of similar elements, FIG. 5 will be explainedreferring to FIG. 3, it should be noted that the embodiment of FIG. 5 isindependent from the embodiment of FIG. 3, and may be implemented usingdifferent devices or designs.

In the embodiments of FIGS. 5, 50 and 51 denote terminals for supplyinga positive supply voltage. For example, in some implementations atterminal 50, a supply voltage of 3 V may be supplied, while at terminal51, a supply voltage of 5 V may be supplied, although in otherembodiments other voltages may also be used.

Furthermore, a terminal 52 may e.g. receive a further supply voltage,e.g. an auxiliary voltage.

A single-ended enable signal may be received at a terminal 53,essentially corresponding to the signal received by terminal 30 of FIG.3. At a terminal 58, a single-ended signal, for example a chip selectsignal, may be received. In this respect, terminal 58 may correspond topad 311 of FIG. 3. Terminals 59 and 510 serve to receive signals from adifferential input like pads 32, 33, which signals may serve to adjust acommon-mode voltage used in a single-ended-to-differential converter526. A terminal 512 corresponds to a ground pin, and terminals 511, 513and 532 may serve to input further control signals. For example, asignal at terminal 532 may be used to provide a bias current for othercomponents in FIG. 5 (e.g. amplifier 527).

The single-ended signal received at terminal 58 is provided to asingle-ended-to-differential converter 526 via a transistor 514.Furthermore, the single-ended signal is provided to an amplifier 519 viaa transistor 57. The single-ended enable signal received at terminal 53is provided to a gate terminal of transistor 57 via a level shifter 55and further to an input of inverter 56. Therefore, transistor 57 enablesor disables forwarding of the single-ended signal to amplifier 519,which, for example, may be implemented as a Schmitt trigger and maycorrespond to Schmitt trigger 315 of FIG. 3. Furthermore, the invertedversion of the enable signal is coupled to a gate terminal of transistor514 to selectively enable forwarding of the single-ended signal tosingle-ended-to-differential converter 526. Therefore, depending on asignal received at terminal 53, the single-ended signal received atterminal 58 is selectively either forwarded to amplifier 519 (forexample if a clock signal or other differential signal is a differentialsignal) or to single-ended-to-differential converter 526 (in case afurther signal, like a clock signal, is a differential signal).

An output signal of single-ended-to-differential converter is fed to adifferential amplifier 527, which may correspond to amplifier 313 ofFIG. 3 in some embodiments. 520 indicates a further inverter invertingthe single-ended enable signal received at terminal 53, and an output ofinverter 520 is fed to an input of an AND-gate 522. Likewise, thesingle-ended enable signal is also fed to an AND-gate 521. AND-gates521, 522 may correspond to AND-gates 314 and 316 of FIG. 3. Furthermore,a NOR-gate 523 followed by an inverter 524 is provided essentiallyimplementing the functionality of gate 317 of FIG. 3, with theadditional possibility of controlling the output by a signal supplied toterminal 54, for example for testing purposes. Elements 533, 515, 516,517, 518, 528, 529, 534 and 530 denote further transistors, some ofwhich form current mirrors for providing a bias current, and 531 denotesa further inverter, which are coupled as illustrated in FIG. 5. Thecircuit implementation shown in FIG. 5 merely serves for illustrating afurther possibility of an embodiment, and other circuit implementationsare equally possible.

FIG. 6 illustrates a circuit diagram of a single-ended-to-differentialconverter according to a further embodiment. For example, FIG. 6 mayrepresent an implementation of single-ended-to-differential converter526 of FIG. 5. To avoid repetitions, the converter of FIG. 6 will bedescribed referring to FIG. 4 in some instances. However, it is to benoted that FIG. 6 is an embodiment independent from the embodiment ofFIG. 4.

In FIG. 6, terminals 60 and 61 may be terminals corresponding toterminals 50 and 51 of FIG. 5 to receive positive supply voltages, forexample a positive supply voltage of 3 V at terminal 60 and a positivesupply voltage of 5 V at terminal 61. Other voltages may also be used.69 denotes a ground terminal, which may correspond to ground terminal512 of FIG. 5. A terminal 62 may be used to provide a bias current forother components in FIG. 6 and may correspond to terminal 532 of FIG. 5.

The single-ended input signal is received at a terminal 621, which maycorrespond to an input terminal of single-ended-to-differentialconverter 526 coupled to terminal 58 via transistor 514 in FIG. 5.Moreover, the signals received at terminals 63, 64 are coupled to anamplifier 610 via resistors 65, 66. Resistors 65, 66 may, for example,correspond to resistors 45, 46 of FIG. 4 and amplifier 610 maycorrespond to amplifier 47 of FIG. 4. A negative input of amplifier 610is coupled to ground via a resistor 611, which may correspond toresistor 48 of FIG. 4. Furthermore, a resistor 613 of FIG. 6 maycorrespond to resistor 49 of FIG. 4 and couples an output of amplifier610 with a negative input of an amplifier 610.

A transistor 67 together with each one of transistors 68, 619 and 620may form essentially current mirrors controlled by the signal atterminal 62. Reference numeral 614 denotes a capacitor providing acapacitive coupling of the output of amplifier 610 with ground.

An output of amplifier 610 is coupled with a resistive dividercomprising resistors 615, 616, 617 and 618. Resistor 615 may correspondto resistors 411 of FIG. 4, resistors 616 and 617 may correspond toresistor 412 of FIG. 4, and resistor 618 may correspond to resistor 413of FIG. 4. A node between resistor 615 and 616 is coupled to a positiveinput of amplifier 622, and a node between resistors 617 and 618 iscoupled with a positive input of amplifier 633. An output of amplifier622 is coupled with a negative input of amplifier 622, and an output ofamplifier 633 is coupled with a negative input of amplifier 633.Amplifiers 622 and 633 may correspond to amplifiers 414, 415 of FIG. 4and may supply signal levels for a differential signal to be generatedhaving a common mode voltage corresponding to a common mode voltage of adifferential signal received at terminals 63, 64.

The output of amplifier 622 is coupled capacitively with ground terminal69 via a capacitor 635, and the output of amplifier 633 is capacitivelycoupled with ground terminal 69 via a capacitor 636.

To convert the single-ended signal received at terminal 622 to adifferential signal, the circuit illustrated in FIG. 6 comprises aslicer 634, for example a Schmitt trigger or amplifier, which maycorrespond to amplifier 410 of FIG. 4 and which may be designed tointroduce a small delay. Furthermore, switches 637 to 640 implemented asT-gates in the example of FIG. 6 are provided, which switches receiveoutput signals from amplifiers 622, 633 and are controlled by an outputsignal of amplifier 634 directly and via an inverter 643. Switches 637to 640 are, therefore, essentially controlled as was explained forswitches 417 to 420 of FIG. 4 to convert the single-ended signal to adifferential signal. The differential signal is then output at terminals641, 642. While FIG. 6 illustrates a specific circuit implementation ofa single-ended-to-differential converter usable in embodiments, thespecific implementation is only given for illustration purposes, and inother embodiments other implementations of single-ended-to-differentialconverters may be employed.

FIG. 7 illustrates a flow chart illustrating a method according to anembodiment. While the method of FIG. 7 is illustrated and will bedescribed as a series of acts or events, the order in which theses actsor events are described is not to be construed as limiting. In otherembodiments, acts or events may occur in a different order than shown,and/or some of the acts or events may be performed in parallel, forexample by different parts of a circuit. The method of FIG. 7 may beimplemented using devices and circuits as illustrated with respect toFIGS. 1 to 6, but is not limited thereto.

At 70, the method of FIG. 7 comprises receiving a first signal. Thefirst signal may be either received as a single-ended signal or adifferential signal, for example a low voltage differential signal.Furthermore, at 71, the method comprises receiving a second signal as asingle-ended signal.

At 72, the method comprises selectively converting the second signal toa differential signal depending on the type of first signal. Forexample, the second signal may be converted to a differential signal,and/or the second signal may be used in a version converted to thedifferential signal, when the first signal is received as a differentialsignal, and not converted to a differential signal or further used as asingle-ended signal in case the first signal is received as asingle-ended signal.

In FIG. 7, the method may comprise further processing of the first andsecond signal (the second signal in the converted version of 72 in casea conversion has been performed or the converted signal is to be used).The further processing may be performed using similar circuits for thefirst and second signals to introduce the same or essentially the samedelays.

Variations, modifications and details discussed with reference to FIGS.1 to 6 may also be applicable to the method of FIG. 7 in a correspondingmanner.

The above described embodiments serve only as examples for furtherillustration and are not to be construed as limiting.

What is claimed is:
 1. An interface device, comprising: a first input toreceive a first signal, a second input to receive a second signal, asingle-ended-to-differential converter coupled to the second input toprovide a differential version of the second signal, and a selectioncircuit adapted to selectively cause either the single-ended secondsignal or the differential version of the second signal to be used forfurther processing depending of a type of the first signal, wherein theselection circuit is adapted to select the single-ended second signalwhen the first signal is a single-ended signal and the differentialversion of the second signal when the first signal is a differentialsignal.
 2. The device of claim 1, further comprising further processingcircuitry to further process the first signal and the second signal,parts of the processing circuitry for processing the first signal havingthe same design as parts of the processing circuitry for furtherprocessing the second signal.
 3. The device of claim 2, wherein theprocessing circuitry comprises at least one Schmitt trigger to processsingle-ended signals.
 4. The device of claim 2, wherein the processingcircuitry comprises at least one differential amplifier to processdifferential signals.
 5. The device of claim 1, wherein the first inputcomprises a clock signal input.
 6. The device of claim 1, wherein thesecond signal comprises a chip select signal.
 7. The device of claim 1,wherein the selection circuit is adapted to selectively provide thesecond signal to the single-ended-to-differential converter.
 8. Thedevice of claim 1, wherein the single-ended-to-differential converter iscoupled to the first input.
 9. The device of claim 8, wherein thesingle-ended-to-differential converter is adapted to provide thedifferential version of the second signal with a common-mode voltageessentially equal to a common-mode voltage of the first signal.
 10. Theinterface device of claim 1, wherein the interface device is amicrosecond channel (MSC) interface device.
 11. A method, comprising:receiving a first signal, receiving a second signal as a single-endedsignal, and selectively converting the second signal to a differentialsignal depending on a type of the first signal, wherein the selectivelyconverting comprises converting the second signal to a differentialsignal if the first signal is a differential signal, and using thesecond signal as single-ended signal if the first signal is asingle-ended signal.
 12. The method of claim 11, further comprisingprocessing the first and second signals based on processing circuitshaving essentially the same delay for the first and second signals. 13.The method of claim 11, wherein the selectively converting comprisesproviding a differential version of the second signal with a common-modevoltage equal to a common-mode voltage of the first signal.
 14. Themethod of claim 11, wherein the first signal comprises a clock signal,and wherein the method further comprises sampling the second signalbased on the first signal.
 15. A device, comprising: a pair ofdifferential clock inputs, a single-ended clock input, a single-endedfurther input, a first amplifier coupled to the differential clockinput, a first Schmitt trigger coupled to the single-ended clock input,a single-ended-to-differential converter coupled to the single-endedfurther input, a second amplifier coupled to an output of thesingle-ended-to-differential converter, a second Schmitt trigger coupledto the single-ended further input, and logic circuitry to selectivelyprovide either a first output signal based on an output of the firstamplifier and a second output signal based on an output of the secondamplifier, or a first output signal based on an output signal of thefirst Schmitt trigger and a second output signal based on an output ofthe second Schmitt trigger at device output terminals.
 16. The device ofclaim 15, wherein the first and second amplifiers have essentially thesame design.
 17. The device of claim 15, wherein the first and secondSchmitt triggers have essentially the same design.
 18. A method,comprising: receiving a first signal, receiving a second signal as asingle-ended signal, selectively converting the second signal to adifferential signal depending on a type of the first signal, wherein theselectively converting comprises converting the second signal to adifferential signal if the first signal is a differential signal, andusing the second signal as single-ended signal if the first signal is asingle-ended signal, wherein the first signal comprises a clock signal,and wherein the method further comprises sampling the second signalbased on the first signal.
 19. The method of claim 18, furthercomprising processing the first and second signals based on processingcircuits having essentially the same delay for the first and secondsignals.
 20. The method of claim 18, wherein the selectively convertingcomprises providing a differential version of the second signal with acommon-mode voltage equal to a common-mode voltage of the first signal.